1966 charging issue

[Taoufiq]

New battery installed. Generator light goes off at arround 1200rpm but battery seems not being charged even at 2300 rpm. I ve installed a voltmeter on the cigarette lighter socked and it s steady at 12.6v.
didnt flight it, test done on ground.
any help?

 

[Bell206]

any help?

What aircraft? I would highly recommend you read up on how the electrical system works first, then get a VOM and verify the voltages noted in the description. If your electrical skills are a bit lacking perhaps get someone with that experience to show you the ropes. Without knowing any of the voltages or lack of voltage readings at the generator, regulator, etc. hard to offer much at this point.

 

[Daleandee]

What aircraft? I would highly recommend you read up on how the electrical system works first, then get a VOM and verify the voltages noted in the description. If your electrical skills are a bit lacking perhaps get someone with that experience to show you the ropes. Without knowing any of the voltages or lack of voltage readings at the generator, regulator, etc. hard to offer much at this point.

It is impossible for anyone here to tell you what the problem is. We could guess for the next two of three pages and eventually someone might be correct.

More seriously, you need a mechanic to assisit you as checking for charging voltages requires the engine to be running (as you know) and you are now working behind a spinning prop unless you have another way to turn the generator/alternator.

12.6 is battery voltage so it is not charging at all. Might be as simple as a broken connector but someone needs to troubleshoot the system. If you don't have the knowledge/tools to do that correctly and safely then hire someone that does. Experience teaches us that throwing parts at the problem is generally more expensive than finding and fixing the problem correctly from the start.

 

[Taoufiq]

What aircraft? I would highly recommend you read up on how the electrical system works first, then get a VOM and verify the voltages noted in the description. If your electrical skills are a bit lacking perhaps get someone with that experience to show you the ropes. Without knowing any of the voltages or lack of voltage readings at the generator, regulator, etc. hard to offer much at this point.

Thanks.
My question is : how is it possible that the generator light goes off at a certain rpm (wich is normal) but the voltage stays at 12.6v?

 

[flyingbrit]

Thanks.
My question is : how is it possible that the generator light goes off at a certain rpm (wich is normal) but the voltage stays at 12.6v?

You have an unusual condition. The light going off means the generator is producing battery voltage.
One explanation is that the regulator's set point is 12.6V instead of the normal 14V. I would "full field" the generator and see what happens. This should isolate the problem to either the generator or regulator.

 

[Bell206]

how is it possible that the generator light goes off at a certain rpm (wich is normal) but the voltage stays at 12.6v?

Depends where the light trigger is located in the over all electrical system, or the overall condition of the electrical system. It could be as simple as a corroded contact or broken wire that gives you this indication.

 

[flyingbrit]

Normally, the generator light is connected across the cutout relay (inside the regulator) contacts. This means one side is at battery voltage, and the other side at generator voltage. Engine off, zero generator voltage, bright light. Engine idling, low voltage from generator, light not so bright. Engine running, generator > 12V, cutout relay closed, light off.

 

[Dan Thomas]

Again, knowing the wiring diagram is essential, and everything else is just throwing money at the problem.

The generator is behaving normally in dousing the light at 1200 RPM. In not raising the voltage to 13.5 or more, I'd suspect that the voltage regulator has been fooled with by someone who doesn't know what they're doing.

And it might also be a cheap multimeter; when making adjustments of this sort one needs a calibrated meter, not some cheap doodad from Harbor Freight or a cigarette lighter voltmeter.

 

[chemgeek]

With the engine running, you should be seeing a typical bus voltage of 13.8-14.2 volts, your regulated charging voltage. So I would strongly suspect some issue with the charging system if your voltage reading of 12.6 V is reliable. (That is a typical voltage for a battery at around 80% charge state.) There are myriad causes for lack of charge voltage, from the alternator/generator itself, the voltage regulator, poor/missing ground connections, etc. It will require some investigation to track down the source of the problem. If the charging system is mis-calibrated to too low a charging voltage, you can permanently damage the battery through excessive sulfation, so it is best to fix this sooner than later.

 

[Dan Thomas]

It will require some investigation to track down the source of the problem. If the charging system is mis-calibrated to too low a charging voltage, you can permanently damage the battery through excessive sulfation, so it is best to fix this sooner than later.

Many mechanics don't understand the charging system, and aircraft owners are even less likely to understand it unless and until they study it and get their minds around it. So when they go fooling with it, thinking they can make it work, they usually make things much worse. And they spend a pile of money doing it.

The cheapest fix is to find a mechanic who is competent in this stuff and hire him. It will get fixed sooner and for a lot less money.

 

[Dan Thomas]

This is how Cessna typically did it:


Note that the master switch has two sets of contacts, and one of them connects the generator field to the regulator's field terminal. Now, if that switch was bad, the generator could not get up enough output to extinguish the warning light at 1200 RPM. Another possibility is a ridiculously easy one: a burned-out Gen fuse.

This is the basic idea:



If the regulator's cutout winding wasn't working, or the contacts shot, the light would go out but nothing would reach the bus (battery).

If the current regulator's contacts were burned out, the field wouldn't get anything and the light wouldn't go out.

If the voltage regulator's contacts were shot, again, the light wouldn't go out, since the field would be getting nothing.

So it's probably a maladjusted regulator, or a bad set of cutout contacts. Or that burned-out fuse. And don't just look at the fuse; they have a bad habit of corroding between the fuse strip and the end caps. Use an ohmmeter. And the contacts in the fuseholder also corrode.

No such thing as a cheap old airplane.

 

[Taoufiq]

It is impossible for anyone here to tell you what the problem is. We could guess for the next two of three pages and eventually someone might be correct.

More seriously, you need a mechanic to assisit you as checking for charging voltages requires the engine to be running (as you know) and you are now working behind a spinning prop unless you have another way to turn the generator/alternator.

12.6 is battery voltage so it is not charging at all. Might be as simple as a broken connector but someone needs to troubleshoot the system. If you don't have the knowledge/tools to do that correctly and safely then hire someone that does. Experience teaches us that throwing parts at the problem is generally more expensive than finding and fixing the problem correctly from the start.

I understand

This is how Cessna typically did it:

View attachment 120627
Note that the master switch has two sets of contacts, and one of them connects the generator field to the regulator's field terminal. Now, if that switch was bad, the generator could not get up enough output to extinguish the warning light at 1200 RPM. Another possibility is a ridiculously easy one: a burned-out Gen fuse.

This is the basic idea:

View attachment 120628

If the regulator's cutout winding wasn't working, or the contacts shot, the light would go out but nothing would reach the bus (battery).

If the current regulator's contacts were burned out, the field wouldn't get anything and the light wouldn't go out.

If the voltage regulator's contacts were shot, again, the light wouldn't go out, since the field would be getting nothing.

So it's probably a maladjusted regulator, or a bad set of cutout contacts. Or that burned-out fuse. And don't just look at the fuse; they have a bad habit of corroding between the fuse strip and the end caps. Use an ohmmeter. And the contacts in the fuseholder also corrode.

No such thing as a cheap old airplane.

thanks a lot for all the info.
In my case, the gen light goes off at 1200rpm…

 

[Taoufiq]

This is how Cessna typically did it:

View attachment 120627
Note that the master switch has two sets of contacts, and one of them connects the generator field to the regulator's field terminal. Now, if that switch was bad, the generator could not get up enough output to extinguish the warning light at 1200 RPM. Another possibility is a ridiculously easy one: a burned-out Gen fuse.

This is the basic idea:

View attachment 120628

If the regulator's cutout winding wasn't working, or the contacts shot, the light would go out but nothing would reach the bus (battery).

If the current regulator's contacts were burned out, the field wouldn't get anything and the light wouldn't go out.

If the voltage regulator's contacts were shot, again, the light wouldn't go out, since the field would be getting nothing.

So it's probably a maladjusted regulator, or a bad set of cutout contacts. Or that burned-out fuse. And don't just look at the fuse; they have a bad habit of corroding between the fuse strip and the end caps. Use an ohmmeter. And the contacts in the fuseholder also corrode.

No such thing as a cheap old airplane.

Thanks for the info. So this morning i polarized the generator on the regulator and it fixed the problem!

 

[Fast Lane]

Dump the generator and go with a Plane Power Alternator conversion. I gave up on never ending generator issues. 5 years with Plane Power and no issues. Always charging. Always clean power. Always exact volts.